基于经颅多普勒信号的搏动性脑动脉血容量估计。
Estimation of pulsatile cerebral arterial blood volume based on transcranial doppler signals.
机构信息
Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, United Kingdom.
Division of Anesthetics, Addenbrooke's Hospital, University of Cambridge, Cambridge, United Kingdom; Section of Neurosurgery, Department of Surgery, University of Manitoba, Winnipeg, Canada; Clinician Investigator Program, University of Manitoba, Winnipeg, Canada.
出版信息
Med Eng Phys. 2019 Dec;74:23-32. doi: 10.1016/j.medengphy.2019.07.019. Epub 2019 Oct 21.
OBJECTIVE
Mathematical modeling of cerebral hemodynamics by descriptive equations can estimate the underlying pulsatile component of cerebral arterial blood volume (CaBV). This way, clinical monitoring of changes in cerebral compartmental compliances becomes possible. Our aim is to validate the most adequate method of CaBV estimation in neurocritical care.
APPROACH
We retrospectively reviewed patients with severe traumatic brain injury (TBI) [admitted from 1992-2012] and continuous transcranial Doppler (TCD) monitoring of cerebral blood flow velocity (FV) displaying either plateau waves of intracranial pressure (ICP), episodes of controlled, mild hypocapnia, or vasopressor-induced increases in arterial blood pressure (ABP). Each cohort was analyzed with continuous flow forward (CFF, pulsatile blood inflow and steady blood outflow) or pulsatile flow forward (PFF, both blood inflow and outflow are pulsatile) modeling approaches for estimating the pulse component of CaBV. Spectral pulsatility index (sPI, the first harmonic of the FV pulse/mean FV) can be estimated using the compliance of the vascular bed (Ca) and the cerebrovascular resistance (CVR - here, Ra). We compared three possible methods of assessing Ca (C1: the CFF model, C2 and C3: the PFF models based on ABP or cerebral perfusion pressure (CPP) pulsations, respectively) and combined them with three possible methods of assessing Ra (Ra1= ABP/FV, Ra2= the resistance area product, and Ra3= CPP/FV). Linear regression techniques were applied to describe the strength of each CaBV estimator (a combination of Ca and Ra) against sPI.
MAIN RESULTS
The combination of C1 and Ra3 (PI_C1Ra3) was the superior descriptor of CaBV as approximated by sPI for both the plateau waves and the hypocapnia cohorts (r = 0.915 and r = 0.955, respectively). The combination of C1 and Ra1 (PI_C1Ra1) was nearly as robust in the vasopressors cohort (r = 0.938 and r = 0.931, respectively).
SIGNIFICANCE
TCD-based estimation of CaBV pulsations seems to be feasible when employing the CFF modeling approach.
目的
通过描述性方程对脑血流动力学进行数学建模，可以估计脑动脉血容量（CaBV）的脉动分量。这样，就可以对脑腔室顺应性的变化进行临床监测。我们的目的是验证在神经危重病学中最适合的 CaBV 估计方法。
方法
我们回顾性分析了 1992 年至 2012 年间因严重创伤性脑损伤（TBI）入院的患者[接受连续经颅多普勒（TCD）监测脑血流速度（FV）]，这些患者的颅内压（ICP）呈平台波、出现可控性、轻度低碳酸血症、或升压药诱导的动脉血压（ABP）升高。每个队列均采用连续流量前向（CFF，脉动血流流入和稳定血流流出）或脉动流量前向（PFF，血流流入和流出均为脉动）建模方法分析，以估计 CaBV 的脉冲分量。可以使用血管床顺应性（Ca）和脑血管阻力（CVR-这里为 Ra）估计谱脉动指数（sPI，FV 脉冲/平均 FV 的第一谐波）。我们比较了三种可能的 Ca 评估方法（C1：CFF 模型，C2 和 C3：分别基于 ABP 或脑灌注压（CPP）脉动的 PFF 模型），并将它们与三种可能的 Ra 评估方法结合（Ra1=ABP/FV，Ra2=阻力面积产物，Ra3=CPP/FV）。线性回归技术用于描述每个 CaBV 估计器（Ca 和 Ra 的组合）与 sPI 的强度。
主要结果
对于平台波和低碳酸血症队列，C1 和 Ra3 的组合（PI_C1Ra3）是最能描述 sPI 近似 CaBV 的指标（r=0.915 和 r=0.955）。在升压药队列中，C1 和 Ra1 的组合（PI_C1Ra1）也非常稳健（r=0.938 和 r=0.931）。
意义
当使用 CFF 建模方法时，TCD 基于 CaBV 脉冲的估计似乎是可行的。
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